US2589212A - Purification of crude ethylene dichloride - Google Patents

Description

March 18, 1952 N. A'. AGAPETUS ETAL PURIFICATION OF' .CRUDE ETHYLENE DICHLORIDE Filed NOV. 8, 1949 f lifflhl.

Patented Mar. 18, 1952 UNITED, STATES PATENT OFFICE PURIFICATION F CRUDE ETHYLENE DICHLORIDE ration of Delaware Application November 8, 1949, Serial No. 126,214

Claims. (Cl. 202-40) 'I'his invention relates to the purication of ethylene dichloride containing varying amounts of water, dichlorodiethylether and other high boiling chlorinated materials.

Ethylene dichloride is produced as a by-product in the production of ethylene oxide by reacting ethylene and chlorine to produce ethylene chlorohydrin which is treated With alkali to produce ethylene oxide. It is also formed by the chlorination of ethylene. As thus formed, as by-product or principal product, it invariably contains impurities, such as Water and high boiling chlorinated materials, many of undetermined composition. Attempts heretofore made to purify such ethylene dichloride by treatment with alkali to neutralize the acidity followed by distillation have resulted in an unmarketable ethylene dichloride, chiefly in that as formed it has or upon standing develops an objectionable acidity. This, it is believed, is chiefly due to the formation of hydrogen chloride by decomposition of the high boilers, which hydrogen chloride contaminates the ethylene dichloride or to the formation of unstable chlorinated compounds which come over with the ethylene dichloride and upon standing form hydrogen chloride, thus imparting an objectionable acidity to the ethylene dichloride product.

It is an object o-f this invention to provide a process of purifying such ethylene dichloride. which process results in a marketable product, which is neutral as produced and which does not develop objectionablet acidity upon standing.

Other objects and advantages of this invention will be apparent from the following detailed description thereof.

In accordance with this invention, the crude ethylene dichloride is purified by distillation in volving three distillation steps. In one step the crude after treatment, to remove acidic constituents, is distilled to drive off the Water. In another step the thus dried material is distilled under relatively mild temperature conditions to drive off as product a substantial proportion of the ethylene dichloride leaving as residue a mixture of ethylene dichloride and higher boiling chlorinated materials. In the other step this residue, with or Without added crude, is distilled under relatively elevated temperature conditions to drive 01T as vapor acidic ethylene dichloride leaving a residue containing residual ethylene dichloride and the higher boiling chlorinated materials. rIChe acidic ethylene dichloride may be treated to remove acidic constituents and produce a stable ethylene dichloride product, or it may be mixed with the crude and the resultant mixture subjected to treatment as hereinabove described.

It Will be understood each of the distillation steps may be carried out continuously or batchwise and that the order of the steps is not critical. Thus, for example, the crude may rst be treated to remove acidic constituents and distilled to drive off the water, the dried material subjected to distillation under mild temperature conditions to drive off the ethylene dichloride and the residue from this latter distillation step subjected to distillation under relatively elevated temperature conditions. Alternatively, the crude may be mixed with the residue from the mild distillation treatment, the mixture subjected to distillation under relatively elevated temperature conditions to separate Wet ethylene dichloride from the higher boiling chlorinated materials, the Wet ethylene dichloride after treatment to remove acidic constituents distilled to drive off water and the dried material subjectedto distillation under mild temperature conditions to produce the product ethylene dichloride.

Surprisingly it has been found that the purification treatments hereinabove described result in the recovery of ethylene dichloride neutral as produced, which remains neutral on standing and which conforms with existing commercial specifications.

In accordance with a preferred embodiment of this invention the crude ethylene dichloride containing varying amounts of water, dichlorodiethylether and other high boiling chlorinated materials, preferably is mixed with the acidic ethylene dichloride distillate from the distillation treatment under the relatively elevated temperature conditions and the mixture subjected to a thorough water Wash or preferably scrubbing with an alkali solution to remove acidic constituents. The neutralized crude ethylene dichloride mixture is then distilled to drive oi the water as a water-ethylene dichloride azeotrope. The vapors taken off overhead are condensed, the condensate stratified, the ethylene dichloride returned to the distillation column as reiiux liquid and the water withdrawn. This distillation is carried out to produce a substantially Water free bottoms product.

Desirably, this distillation to effect removal of Water is `carried out in a continuous fractionating column and a small stream of Water is continuously added to insure the presence of suicient water to form water ethylene dichloride azeotrope in the upper portion of the column. The addition of .1% to 1% of water vfor rthis purpose.

based on the weight of the feed to the column during this distillation will be found adequate. The added Water makes for smoother operation of the column and assists in the removal of hydrogen chloride -which leaves the system dissolved in the aqueous phase separated from the ethylene dichloride phase which is returned to the column.

The residue from the aforesaid distillation substantially free of water is distilled underrelatively mild conditions of temperature to drive olf ethylene dichloride vapors which are condensed leaving a residue containing from 30% to r70%, preferably about 50%, of ethylene dichloride. In this distillation step from 60% to 80% of the feed to the column is taken off overhead; the residue therefore consists of from 20% to 40% of the feed. The condensate from this distillation is a high-purity neutral ethylene dichloride which retains its neutrality on standing.

The residue from the mild distillation treatment with lor without the addition thereto of 'Some `of .the crude is distilled under relatively elevated temperature conditions to drive off most ofthe ethylene dichloride leaving a residue containing from about 3% to 20%, 'preferably about by weight of ethylene dichloride, the rest being'higher boiling 'chlorinated materials. From about 20%"to 65% of the feed to the column may be "t'ak'e'n oif overhead as acidic ethylene dichloride; from 35% to 80% of the feed is left as residue'which is useful as a solvent for metal cleaning `and degreasing and as a notation agent. The ethylene dichloride vapors taken off overhead are condensed and the acidic ethylene dichloride condensate thus produced either added to the crude, ashereinabove described, or subjected to a water wash and drying treatment to `produce a high-purity neutral ethylene dichloride which retains its Aneutrality on standing.

A-Desirably, a small stream of water is continuously Yadded -to the column during the distillation under relatively elevated temperature conditions resulting in the production of a residue containing from 3% to 20%, preferably about 10%, ethylene dichloride. The added water makesfor smoother operation of the column and assists in the removal of hydrogen chloride. As in the azeotropic distillation step from .1% to 1% of Water based on the Weight of the feed may be added to the column for this purpose.

While, as above indicated, the crude admixed with the distillate from the relatively mild distillation treatment and the acidic ethylene dichloride from the relatively high temperature distillation treatment may be subjected to a thorough water Wash to elfect removal of acidic constituents it is preferred to scrub with alkali to effect this treatment. An aqueous solution or slurry of a hydroxide, carbonate or bicarbonate of an alkali or alkaline earth metal may be used In general a small excess of alkali'should be used over and above the amount required to Agive a completely neutralized mixture. From an economy standpoint a solution o'f sodium hydroxide or carbonate is preferred.

The distillation rtreatments may be carried out continuously in three or more columns, the alkali scrubbed crude mixture being introduced, for example;continuously into the iirst column to which water is added continuously, the mixture subjected to 'azeotropic distillation with continuous return of the ethylene dichloride phase to the top 'of the column, and the dry crude ethylene 'dichloride'withdrawn continuously from the bottom of the column and introduced into a second column in which it is subjected to distillation under relatively mild temperature conditions. From the top of this second column the vapors are condensed producing a continuously iiowing stream of ethylene dichloride product. Residue from this second column is withdrawn continuously and introduced into a third column where it is subjected to a relatively high temperature treatment. Acidic ethylene dichloride is taken off overhead from this third column and the residue containing from about 3% to about 20% ethylene dichloride and higher boiling chlorinated materials is withdrawn continuously from the base of this column.

Alternatively, the process may be operated batchwise using one or more distillation columns. Thus, abatch of 'the neutralized mixture containing the crude is subjected to distillation in a column to drive on the water, the ethylene dichloride phase separated from the water phase and returned to the top of the column. The residue from this distillation is subjected to distillation in the same or a different column under mild temperature conditions to produce the desired ethylene dichloride product leaving a residue which is subjected to distillation under relatively elevated temperature conditions in the same or a different column. Acidic ethylene dichloride is thus taken off overhead leaving a residue containing the higher boiling chlorinated materials.

The distillation is preferably carried out under atmospheric pressure conditions, although subor super-atmospheric pressure conditions may be used, if desired. Operating under atmospheric pressure conditions the still pot or bottom of the column is maintained at a temperature of from 275 to 350 F. during the distillation carried out under relatively elevated teinperatures, from 200-260 F. during the azeotropic distillation to eifect removal of water and from 2'l0 to 260 F. during the mild distillation treatment. Operating under vacuum conditions these temperatures may be lower depending upon the degree of vacuum.

This invention will be illustrated by an example of its application to the treatment of ethylene dichloride produced as a by-product in the chlorohydrination of ethylene.

Ethylene chlorohydrin has for a long time been manufactured on a large scale for use as an intermediate in the manufacture of ethylene oxide and ethylene glycol. A common method of making ethylene chloroliydrin is by allowing ethylene to react with an aqueous solution of hypochlorous acid. Since hypochlorous acid is formed by interaction of chlorine and Water, it has long been the practice to manufacture ethylene chlorohydrin simply by passing ethylene and chlorine simultaneously into water. By continually withdrawing the solution as formed, and replacing with additional water, it has been practical to operate a continuous process for the manufacture of ethylene chlorohydrin.

When ethylene chlorohydrin is manufactured by this reaction, a certain amount of water insoluble by-product material is invariably formed. While the relative amount of water insoluble byproduct depends to some extent on reaction conditions such as temperature, concentration of chlorohydrin solution being produced, etc., it is not practical to operate such a commercial process of ethylene chlorohydrin manufacture without production of substantial amounts of this by-produot material. Ordinarily, somewhere between 5% and 20% of the chlorine charged to the chlorohydrinator takes part in the reactions leading to the formation of these Water insoluble by-product materials. The chief component of the water insoluble by-product materials referred to above is ordinarily ethylene dichloride but, in addition, there are ordinarily substantial amounts 2,2dichlorodiethy1 ether, higher chlorinated ethane compounds, etc. This mixture of water-insoluble chlorinated by-products is referred to hereinafter as crude dichloride.

The unreacted gases passing out of a chlorohydrination reactor will in general be nearly saturated with dichloride vapors; this dichloride may be recovered by scrubbing these off-gases with a relatively non-volatile solvent such as gas oil, and then distilling the absorbed dichloride from the scrubber liquid.

A certain proportion of the crude dichloride will separate and form a distinct phase which may be removed from the aqueous chlorohydrin solution by use of a decanter. However, a portion will also remain dissolved in the ethylene chlorohydrin solution, and it is also generally found that it is impracticable to separate by gravity all of the dichloride phase so that a substantial portion of these by-products remains in the ethylene chlorohydrin solution as formed. One method of separating the crude dichloride from vthe aqueous chlorohydrin is to subject the solution to a preliminary steam distillation as disclosed in the Heard Patent 2,103,849, according to which one can effect a removal of the crude dichlorides by vaporizing about 5% of the Water of the charge, and then subsequently removing the bulk of the chlorohydrin by continuing the steam distillation. However, it is frequently not desired to concentrate the chlorohydrin solution before use, and the dilute solution of aqueous ethylene chlorohydrin obtained by passing ethylene and chlorine simultaneously through water may be used directly for the manufacture of ethylene oxide by mixing it while hot with an alkali such as a lime slurry. The ethylene chlorohydrin reacts with the lime to form calcium chloride which remains in the solution and ethylene oxide which is very volatile and can be separated from the mixture by distillation. In such a process, it is normally found that the crude ethylene oxide so distilled contains some of the crude dichloride referred to above. Ordinarily, a substantial portion of this dichloride will separate as a distinct liquid phase from the crude ethylene oxide condensate. However, a certain proportion of the crude dichloride present will remain dissolved in the ethylene oxide layer and will have to be separated at a later stage. It is generally found that redistillation of the crude ethylene oxide condensate will eiectively remove the last traces of dichlorides. By fractional distillation of this crude ethylene oxide condensate it is possible to recover overhead a dry high-purity ethylene oxide product; from the bottom of the column water and crude dichloride are withdrawn and passed to a decanter from which the last of the crude dichloride can be recovered. While the relative compositions of the dichloride product separated by the several means enumerated above will differ one from another, they are generally so similar that it is preferable to mix the several streams to produce the crude ethylene dichloride subjected to purification.

In the drawing, which is a ow sheet indicating the steps involved in the practice of a preferred embodiment of this invention, I0 repmeans at its base.

resents a collecting tank in which crude dichloride drawn from any or all of the sources above mentioned are mingled. The crude dichloride is Withdrawn through line II and is pumped by a pump I2 through a line I3 into a scrubber I4. A line I5 leads from a condenser I6 communieating with a fractionating volumn I1 through which line I5 condensate from condenser I6 is pumped by a pump I8 into the scrubber I4. The mixture of crude ethylene dichloride and the condensate from condenser I6 is scrubbed with Water or alkali in scrubber I4 to remove acidic constituents; the water or alkali may be supplied to the scrubber through line I9. From the scrubber I4 the treated mixture is pumped by pump 20 through line 2| into a distillation column 22 where it is subjected to distillation.

Water is continuously added during the distillation taking place in column 22 through a line 23 to maintain vapors of water-ethylene dichloride azeotrope in the top of the column 22. The vapors passing off overhead through line 23 enter condenser 24 where they are condensed. The condensate passes into a decanter 25 which is provided With a line 26 for return of the ethylene dichloride lower layer. The upper layer of Water is continuously withdrawn from decanter 25 through a line 21.

The substantially Water-free bottoms product from column 22 flows .through a line 28 communicating with a pump 29 for pumping the product through a line 30 into a column 3I Where it is subjected to distillation. The ethylene dichloride vapors are taken off overhead through line 32 which communicates with a condenser 33. Ethylene dichloride product is Withdrawn through line 34 leading from condenser 33. From the bottom of column 3| line 35 having pump 36 therein leads to column Il. This column is provided With an overhead line 37 communicating with condenser !6 and a bottoms draw-olf line 38.

. Each of the columns Il, 22 and 3|, desirably, is of the conventional bubble cap and plate type and is provided with steam or other heating The columns are preferably operated under atmospheric pressure conditions, although, as indicated above, sub or super atmospheric pressure conditions may be employed.

The following example is given for purposes of illustration only, it will be understood this invention is not limited to this example.

Crude ethylene dichloride from tank I0 containing Water, dichlorodiethylether and other high boiling chlorinated materials is mixed with the condensate from condenser I6 the crude contains about 15% by Weight of high boiling chlorinated materials. This mixture is scrubbed with dilute sodium hydroxide, employing 0.01-0.02 gallon of sodium hydroxide solution of 10% concentration per gallon of mixture. The thus neutralized mixture is then distilled under atmospheric pressure in column 22 while adding .33%

which remains neutral upon standing. The residue containing about 50% ethylene dichloride is pumped through line 35 into column I1. The bottoms temperature in column I1 is 335-340 F. and the overhead temperature 180 F. From the bottom is removed through line 38 a residue containing 10% ethylene dichloride. The overhead vapors are condensed in condenser I6 and the condensate pumped through line I into scrubber I4 Where it is mixed with the incoming crude.

In the above example about 70% by weight of the feed comes off as product through line 34,

about 16% is recovered as by-product and removed from the process through line 38 and about 13% is recirculated through line I5.

In lieu of the preferred procedure hereinabove described, the crude ethylene dichloride is mixed with the residue from the distillation treatment under mild temperature conditions. This mixture is subjected to distillation under relatively elevated temperature conditions to drive off overhead wet acidic ethylene dichloride free of higher boiling chlorinated materials. The residue thus produced contains from 3% to 20%, preferably about ethylene dichloride the rest being the higher boiling chlorinated materials.

The wet acidic ethylene dichloride with added crude is then washed with a solution of caustic soda to neutralize acidic constituents and the neutralized material subjected to azeotropic distillation, preferably with addition of water to the column. Overhead from this column is stratiiied into a water layer which may be discarded, and an ethylene dichloride layer which is returned to the column as reflux, as hereinabove described. The bottoms product withdrawn from this distillation is dry, acid-free ethylene dichloride containing, however, a small amount of higher boiling materials.

The dry, acid-free dichloride is subjected to fractional distillation under mild temperature conditions. Product ethylene dichloride is tak-- en oii overhead, as hereinabove described. The residue from this distillation containing from 30% to 70%, preferably about 50%, ethylene dichloride may be mixed with the cr-ude and the mixture subjected to distillation under relatively elevated temperature conditions.

It will be noted this invention provides an improved process oi producing ethylene dichloride meeting commercial specifications and which does not lose its neutrality upon standing and this with little loss in yield. The actual loss of dichloride in the process diagrammatically illustrated in the drawing is equal to the amount of dichloride present in the residue from column I'I, which residue may contain as little as 3% ethylene dichloride and preferably contains about 10% so that the loss is small. Further, this residue does have utility and may be sold as such.

Since certain changes may be made in carrying out the above process Without departing from the scope of the invention it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. The process of purifying crude ethylene dichloride, which comprises at least three distillation treatments, in one of which the crude is distilled at a still bottom temperature corresponding to a temperature of from 200 to 260 F. under atmospheric pressure to separate the Water therefrom, in another of which the substantially water-free crude is subjected to distillation at a still bottom temperature corresponding to a temperature of from 210 to 260 F. under atmospheric pressure to drive o overhead purified ethylene dichloride product containing from 30% to 70% of the ethylene dichloride in the water- `free crude subjected to distillation, and in the third of which the residue from the distillation at a still bottom temperature of from 210 to 260 F. is subjected to distillation at a still bottom temperature corresponding to a temperature of from 275 to 350 F. under atmospheric pressure to effect separa-tion of ethylene dichloride from higher boiling chlorinated materials.

2. In the process of purifying ethylene dichloride saturated with Water the improvement which comprises continuously feeding a stream of crude ethylene dichloride saturated with water to a distillation column; continuously introducing a stream of Water into said column, continuously taking off overhead vapors of an azeotropic mixture of ethylene dichloride and Water; continuously condensing the vapors, stratifying the condensate into water and ethylene dichloride layers, removing the water and returning the ethylene dichloride to the distillation column; and continuously removing from said distillation column a bottoms ethylene dichloride product which is substantially free of Water.

3. The process of purifying crude ethylene dichloride which comprises treating the crude to remove acidic constituents therefrom, distilling the thus treated crude at a still bottom temperature of from 200 to 260 F. under atmospheric pressure to effect separation of Water therefrom, removing the water-free ethylene dichloride as residue from the aforesaid distillation treatment, distilling the same at a still bottom temperature of from 210 to 260 F. under atmospheric pressure to drive off from 30% to 70% of the ethylene dichloride as vapor, condensing the ethylene dichloride vapor thus driven-off and subjecting the residue to distillation at a still bottom temperature of from 275 to 350 F. under atmospheric pressure to effect separation of ethylene dichloride from higher boiling chlorinated materials.

4. The process of purifying ethylene dichloride produced in the chlorohydrination of ethylene and containing water, dichlorodiethylether and other high boiling chlorinated materials, which comprises, step 1, mixing the crude ethylene dichloride with the condensate from step 5 hereinafter set forth; step 2, neutralizing acidic constituents in the resultant mixture; step 3, distilling the neutralized mixture from step 2 at a still bottom temperature of from 200 to 260 F. under atmospheric pressure to drive oiI as vapor an azeotrope of water and ethylene dichloride, condensing the vapor, stratifying the condensate into ethylene dichloride and water layers, returning the ethylene dichloride to the distillation column and withdrawing as residue a bottoms product substantially free of Water; step 4, distilling the bottoms product from step 3 at a still bottom temperature of from 210 to 260 F. under atmospheric pressure to drive off overhead from 30% to 70% of the ethylene dichloride as neutral product and produce a residue containing residual ethylene dichloride and higher boiling chlorinated materials; and step 5, subjecting the residue from step 4 to distillation at a still bottom temperature of from 275 to 350 F. under atmospheric pressure to drive oif overhead acidic ethylene dichloride vapor and leave a residue containing a minor proportion of ethylene dichloride and higher boiling chlorinated materials, condensing the acidic ethylene dichloride vapor and using the condensate in step 1 for admixture with the crude ethylene dichloride.

5. The process as deiined in claim 4, in which in step 3 additional water is added to the distillation column.

6. The process of purifying ethylene dichloride produced in the chlorohydrination of ethylene and containing water, dichlorodiethylether and other high boiling chlorinated materials, which comprises, step 1, mixing the crude ethylene dichloride with the condensate from step hereinafter set forth; step 2, treating the resultant mixture with alkali to neutralize acidic constituents; step 3, distilling the neutralized mixture from step 2 while maintaining a bottoms temperature of 200 to 260 F. under atmospheric pressure to drive off as vapor an azeotrope of water and ethylene dichloride, condensing the vapor, stratifying the condensate into ethylene dichloride and Water layers, returning the ethylene dichloride to the distillation column and withdrawing as residue a bottoms product substantially free oi water; step 4, distilling the bottoms product from step 3 while maintaining a bottoms temperature of 210 to 260 F. under atmospheric pressure to drive 01T overhead from 30% to 70% of the ethylene dichloride and prod-uce a residue containing residual ethylene dichloride and higher boiling chlorinated materials; and step 5, subjecting the residue from step 4 to distillation while maintaining a bottoms temperature of 275 to 350 F. under atmospheric pressure to drive off overhead acidic ethylene dichloride vapor and leave a residue containing from 2% to 20% ethylene dichloride and higher boiling chlorinated materials, condensing the acidic ethylene dichloride vapor and using the condensate in step 1 for admixture with the crude ethylene dichloride.

7. The process as defined in claim 6, in which in step 3 from .1% to 1% of water based on the weight of the feed is added to the column.

8. The process of purifying ethylene dichloride produced in the chlorohydrination of ethylene and containing water, dichlorodiethylether and other high boiling chlorinated materials, which comprises, step 1, mixing the crude ethylene dichloride with the residue from step 5 hereinafter set forth; step 2, distilling the resultant mixture while maintaining a bottoms temperature of 275 to 350 F. under atmospheric pressure to drive off as vapor substantially all of the water, the major portion of the ethylene dichloride and produce a residue containing from 3% to 20% of ethylene dichloride and higher boiling chlorinated materials and condensing the vapors; step 3, treating the condensate from step 2 with alkali to neutralize acidic constituents; steps 4, distilling the neutralized material from step 3 while maintaining a bottoms temperature of from 200 to 260 F. under atmospheric pressure to drive off as vapor an azeotrope of water and ethylene dichloride, condensing the vapor, stratifying the condensate into ethylene dichloride and Water layers, returning the ethylene dichloride to the distillation column, withdrawing the water and withdrawing from the distillation column a bottoms product substantially free of water; and step 5, subjecting the bottoms product from step 4 to distillation While maintaining a bottoms temperature of from 210 to 260 F. under atmospheric pressure to drive oi overhead from 30% to 70% of the ethylene dichloride as product and produce a residue which is used in step 1.

9. The process as defined in claim 8, in which in step 4 from .1% to 1% of water based on the Weight of the feed is added to the distillation column.

10. In the process of purifying ethylene dichloride saturated with water, the improvement which comprises introducing into the distillation column from .1% to 1% by weight of additional water based on the weight of the saturated ethylene dichloride introduced into the column, distilling, taking oi overhead vapors of an azeotropic mixture of ethylene dichloride and water, condensing the vapors, stratifying the condensate into ethylene dichloride and water layers, returning ethylene dichloride to the distillation column, removing the water, and withdrawing from the column a bottoms product substantially free of water.

NAPOLEON A. AGAPETUS ROBERT REPP REESE. LOREN P. SCOVILLE.

REFERENCES CITED The following references are of record in the i'lle of this patent:

UNITED STATES PATENTS Number Name Date 2,022,616 Berliner Nov. 26, 1935 2,353,563 I-Iemminger July 11, 1944 2,356,785 Hammond Aug. 29, 1944 2,359,860 Kiefer et al Oct. 10, 1944

Claims (2)

1. THE PROCESS OF PURIFYING CRUDE ETHYLENE DICHLORIDE, WHICH COMPRISES AT LEAST THREE DISTILLATION TREATMENTS, IN ONE OF WHICH THE CRUDE IS DISTILLED AT A STILL BOTTOM TEMPERATURE CORRESPONDING TO A TEMPERATURE OF FROM 200* TO 260* F. UNDER ATMOSPHERIC PRESSURE TO SEPARATE THE WATER THEREFROM, IN ANOTHER OF WHICH THE SUBSTANTIALLY WATER-FREE CRUDE IS SUBJECTED TO DISTILLATION AT A STILL BOTTOM TEMPERATURE CORRESPONDING TO A TEMPERATURE OF FROM 210* TO 260* F. UNDER ATMOSPHERIC PRESSURE TO DRIVE OFF OVERHEAD PURIFIED ETHYLENE DICHLORIDE PRODUCT CONTAINING FROM 30% TO 70% OF THE ETHYLENE DICHLORIDE IN THE WATERFREE CRUDE SUBJECTED TO DISTILLATION, AND IN THE THIRD OF WHICH THE RESIDUE FROM THE DISTILLATION AT A STILL BOTTOM TEMPERATURE OF FROM 210* TO 260* F. IS SUBJECTED TO DISTILLATION AT A STILL BOTTOM TEMPERATURE CORRESPONDING TO A TEMPERATURE OF FROM 275* TO 350* F. UNDER ATMOSPHERIC PRESSURE TO EFFECT SEPARATION OF ETHYLENE DICHLORIDE FROM HIGHER BOILING CHLORINATED MATERIALS.

10. IN THE PROCESS OF PURIFYING ETHYLENE DICHLORIDE SATURATED WITH WATER, THE IMPROVEMENT WHICH COMPRISES INTRODUCING INTO THE DISTILLATION COLUMN FROM .1% TO 1% BY WEIGHT OF ADDITIONAL WATER BASED ON THE WEIGHT OF THE SATURATED ETHYLENE DICHLORIDE INTRODUCED INTO THE COLUMN, DISTILLING, TAKING OFF OVERHEAD VAPORS OF AN AZEOTROPIC MIXTURE OF ETHYLENE DICHLORIDE AND WATER, CONDENSING THE VAPORS, STRATIFYING THE CONDENSATE INTO ETHYLENE DICHLORIDE AND WATER LAYERS, RETURNING ETHYLENE DICHLORIDE TO THE DISTILLATION COLUMN, REMOVING THE WATER, AND WITHDRAWING FROM THE COLUMN A BOTTOMS PRODUCT SUBSTANTIALLY FREE OF WATER.

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